Method and apparatus for controlling wireless power transmission

ABSTRACT

Disclosed are a method of controlling wireless power transmission and an apparatus therefor. A method of controlling wireless power transmission of a wireless power transmitter includes a first packet reception phase of receiving a foreign object detection status packet, a first determination phase of determining whether the foreign object is present based on the foreign object detection status packet, and a power control phase of controlling power based on a determination result of the first determination phase, wherein the power control phase includes a first power transfer mode for transmitting first power upon determining that the foreign object is present as the determination result of the first determination phase, and a second power transfer mode for transmitting second power upon determining that the foreign object is not present as the determination result of the first determination phase.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to Korean PatentApplication No. 10-2018-0068751, filed in Korea on Jun. 15, 2018, whichis hereby incorporated in its entirety by reference as if fully setforth herein.

TECHNICAL FIELD

Embodiments relate to a wireless power transmission technology, and moreparticularly, to a method and apparatus for controlling wireless powertransmission for wireless charging.

BACKGROUND

Recently, with rapid development of information and communicationtechnology, a society based on ubiquitous information and communicationtechnology has been formed.

In order to connect information and communication apparatuses anywhereand anytime, sensors each having a computer chip having a communicationfunction need to be installed in all social facilities. Accordingly,problems related to supply of power to such apparatuses or sensors havenewly arisen. In addition, as portable apparatuses such as mobilephones, Bluetooth handsets and music players such as iPod have rapidlyincreased, it takes time and effort for a user to charge batteries. As amethod for solving such a problem, recently, wireless power transmissiontechnology is attracting considerable attention.

Wireless power transmission or wireless energy transfer technologyrefers to technology of wirelessly transmitting electric energy from atransmitter to a receiver using the principle of magnetic induction. Inthe 1800s, electrical motors or transformers using the principle ofelectromagnetic induction already started to be used and then methods ofradiating radio waves or electromagnetic waves such as lasers andtransmitting electric energy were also attempted. Commonly used electrictoothbrushes or electric razors are charged using the principle ofelectromagnetic induction.

Up to now, a wireless energy transfer method may be roughly divided intoa magnetic induction method, an electromagnetic resonant method and apower transmission method using a short-wavelength radio frequency.

The magnetic induction method refers to technology of using a phenomenonthat, when two coils are adjacently placed and current is supplied toone coil, a magnetic flux is generated to generate electromotive forcein the other coil, and is commercially available in small apparatusessuch as mobile phones. The magnetic induction method may transmit powerof a maximum of several kilowatts (kW) and has high efficiency. However,since a maximum transmission distance is 1 cm or less, an apparatusshould be generally located to be adjacent to a charger.

The magnetic induction method uses an electric field or a magnetic fieldinstead of electromagnetic waves or current. The magnetic inductionmethod is hardly influenced by an electromagnetic wave and thus isharmless to other electronic apparatuses and humans. In contrast, themagnetic induction method may be used at a limited distance and in alimited space and energy transfer efficiency is slightly low.

The short-wavelength wireless power transmission method—briefly referredto as an RF method—uses a method of directly transmitting and receivingenergy in the form of radio waves. This technology is an RF typewireless power transmission method using a rectenna. Rectenna means is acompound word of “antenna” and “rectifier” and means an element fordirectly converting RF power into direct current (DC) power. That is,the RF method is technology of converting AC radio waves into DC radiowaves and using DC radio waves and, recently, research intocommercialization thereof has been actively conducted as efficiency isimproved.

Wireless power transmission technology may be variously used in IT,railroad and consumer-electronics in addition to the mobile industry.

If a conductor which is not a wireless power receiver—that is, a foreignobject (FO)—is present in a wireless charging area, an electromagneticsignal received from a wireless power transmitter may be induced in theFO. For example, the FO may include coins, clips, pins, and ballpointpens.

If an FO is present between a wireless power receiver and a wirelesspower transmitter, wireless charging efficiency may be significantlylowered, and the temperatures of the wireless power receiver and thewireless power transmitter may increase due to increase in ambienttemperature of the FO. If the FO located in the charging area is notquickly removed, power waste may occur and the wireless powertransmitter and the wireless power receiver may be damaged due tooverheating.

Even if an FO is not present in an actual charging area, when a wirelesspower transmitter incorrectly determines that an FO is present in acharging area, charging may be stopped.

Accordingly, accurate detection of the FO on a charging area is becomingan important issue in wireless charging technology.

SUMMARY

Embodiments provide a method and apparatus for controlling wirelesspower transmission for wireless charging.

Embodiments provide a wireless power transmitter for more accuratelydetecting a foreign object.

Embodiments provide a method and apparatus for controlling wirelesspower transmission for minimizing foreign object detection error toprevent unnecessary stop of charging.

Further, embodiments provide a wireless power transmitter for preventinga device from being damaged due to a foreign object and for seamlesscharging through adaptive transmission power control according towhether the foreign object is present.

Additional advantages, objects, and features of embodiments of thedisclosure will be set forth in part in the description which followsand in part will become apparent to those having ordinary skill in theart upon examination of the following or may be learned from practice ofembodiments of the disclosure. The objectives and other advantages ofembodiments of the disclosure may be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

Embodiments provide a method of controlling wireless power transmissionand apparatuses therefor.

In one embodiment, a method of controlling wireless power transmissionof a wireless power transmitter includes a first packet reception phaseof receiving a foreign object detection status packet, a firstdetermination phase of determining whether the foreign object is presentbased on the foreign object detection status packet, and a power controlphase of controlling power based on a determination result of the firstdetermination phase, wherein the power control phase includes a firstpower transfer mode for transmitting first power upon determining thatthe foreign object is present as the determination result of the firstdetermination phase, and a second power transfer mode for transmittingsecond power upon determining that the foreign object is not present asthe determination result of the first determination phase.

The second power may be greater than the first power, and power betweenthe first power and the second power may be increasingly or decreasinglytransmitted based on a change in a power transmission environment in thesecond power transfer mode.

The first power may be 5 W.

The second power may be 15 W.

The method may further include a second determination phase ofdetermining whether the foreign object is present in the first powertransfer mode.

The second determination phase may include at least one of a thirddetermination phase of determining whether the foreign object is presentbased on loss of transmission power, or a fourth determination phase ofdetermining whether the foreign object is present based on a temperaturechange.

The third determination phase may include measuring intensity of thetransmission power, receiving information on intensity of receptionpower corresponding to the transmission power from a wireless powerreceiver, estimating power loss based on a difference value between theintensity of the transmission power and the intensity of the receptionpower, and comparing the estimated power loss with a predetermined powerloss reference value to determine whether the foreign object is presentfor a predetermined time period.

The fourth determination phase may include measuring temperature of acharging area, calculating a temperature change for a predetermined timeperiod based on the measured temperature, and comparing the calculatedtemperature change with a predetermined temperature change referencevalue to determine whether the foreign object is present.

As a determination result of the second determination phase, when theforeign object is determined to be present, power transmission may bestopped, and as the determination of the second determination phase,when the foreign object is not determined to be present, the first powertransfer mode may be changed to the second power transfer mode.

In another embodiment, a method of controlling wireless powertransmission of a wireless power transmitter includes a first packetreception phase of receiving a foreign object detection status packet, afirst determination phase of determining whether the foreign object ispresent based on the foreign object detection status packet, a phase oftransmitting first power upon determining that the foreign object ispresent as a determination result of the first determination phase, aphase of transmitting power between the first power and the second powerwhen the foreign object is not present as the determination result ofthe first determination phase, and a second determination phase ofdetermining whether the foreign object is present in the phase oftransmitting the first power, wherein the second determination phaseincludes at least one of a third determination phase of determiningwhether the foreign object is present based on loss of transmissionpower, or a fourth determination phase of determining whether theforeign object is present based on a temperature change.

In another embodiment, a wireless power transmitter includes an antennaconfigured to wirelessly transmit power, a demodulator configured todemodulate a signal including a foreign object detection status packetreceived from the antenna, and a controller configured to determinewhether the foreign object is present, wherein the controller performs afirst determination phase of determining whether the foreign object ispresent based on the foreign object detection status packet, performscontrol to transmit first power upon determining that the foreign objectis present as a result of the first determination phase, and performscontrol to transmit power between the first power and the second powerupon determining the foreign object is not present as the determinationresult of the first determination phase.

The controller may perform a second determination phase of determiningwhether the foreign object is present during transmission of the firstpower upon determining that the foreign object is present as a result ofthe first determination phase.

The second determination phase may include at least one of a thirddetermination phase of determining whether the foreign object is presentbased on loss of transmission power, or a fourth determination phase ofdetermining whether the foreign object is present based on a temperaturechange.

The wireless power transmitter may further include a sensor configuredto measure intensity of the transmission power and to transmit theintensity of the transmission power to the controller, wherein, in thethird determination phase, the controller may receive information onintensity of reception power corresponding to the transmission powerthrough the demodulator, may estimate power loss based on a differencevalue between the intensity of the transmission power and the intensityof the reception power, and may compare the estimated power loss with apredetermined power loss reference value to determine whether theforeign object is present for a predetermined time period.

The sensor may measure temperature and may transmit information on thetemperature to the controller, and in the fourth determination phase,the controller may calculate a temperature change for a predeterminedtime period based on the measured temperature, and may compare thecalculated temperature change with a predetermined temperature changereference value to determine whether the foreign object is present.

As a determination result of the second determination phase, when theforeign object is determined to be present, the controller may stoppower transmission, and as determination of the second determinationphase, when the foreign object is not determined to be present, thecontroller may perform control to transmit power between the first powerand the second power.

The second power may be greater than the first power, and the firstpower may be 5 W.

In another embodiment, a method of controlling wireless powertransmission of a wireless power transmitter includes a first packetreception phase of receiving a foreign object detection status packet, afirst determination phase of determining whether the foreign object ispresent based on the foreign object detection status packet, and a firstpower adjustment phase of adjusting power based on a determinationresult of the first determination phase.

The first power adjustment phase may include maintaining guaranteedpower to second power as initial setting when the foreign object is notpresent as a determination result of the first determination phase, anddownward-adjusting the guaranteed power from the second power to firstpower when the foreign object is present as a determination result ofthe first determination phase.

The first power may be equal to or less than 5 W.

The second power may be equal to or less than 15 W.

The method may further include a power transfer phase of performingcharging based on the adjusted power and a second determination phase ofdetermining whether the foreign object is present in the power transferphase.

The second determination phase may include a third determination phaseof determining whether the foreign object is present based on theestimated power loss during charging, wherein, when the foreign objectis present as a determination result of the third determination phase,the performed charging may be stopped.

The third determination phase may include measuring intensity oftransmission power during charging, receiving information on receptionpower corresponding to the transmission power from a wireless powerreceive, estimating power loss based on a difference value betweenintensity of the transmission power and intensity of the receptionpower, and comparing the estimated power loss with a predetermined powerloss reference value to determine whether the foreign object is presentfor a predetermined time period.

The second determination phase may include a fourth determination phaseof determining whether the foreign object is present based on atemperature change during charging, wherein, when the foreign object ispresent as a determination result of the fourth determination phase, theperformed charging may be stopped.

The fourth determination phase may include measuring temperature of acharging area, calculating a temperature change for a predetermined timeperiod based on a result of the measuring of the temperature, andcomparing the calculated temperature change with a predeterminedtemperature change reference value to determine whether the foreignobject is present.

The method may further include a renegotiation phase of resettingguaranteed power by renegotiating a power transfer contract when theforeign object is not present as a determination result of the thirddetermination phase or the fourth determination phase.

The second determination phase may include a third determination phaseof determining whether the foreign object is present based on theestimated power loss during charging, and a fourth determination phaseof determining whether the foreign object is present based on atemperature change measured during charging when the foreign object ispresent as a determination result of the third determination phase,wherein power transmission for charging may be stopped for thepredetermined time period when the foreign object is present as adetermination result of the fourth determination phase.

The method may further include transmitting a response based on adetermination result of the first determination phase, wherein theresponse may be a response indicating that the foreign object ispresent, and when currently set guaranteed power is greater than firstpower, intensity of power may be downward-adjusted to the first power orless.

The first power may be 5 W.

The first determination phase may include determining a quality factorthreshold value based on a reference quality factor value included inthe foreign object detection status packet and comparing a premeasuredquality factor value with the quality factor threshold value todetermine whether the foreign object is present.

In another embodiment, a wireless power transmitter may include atransmission antenna configured to wirelessly transmit power, ademodulator configured to demodulate a signal of the transmissionantenna and to receive a foreign object detection status packet, and acontroller configured to determine whether the foreign object is presentbased on the demodulated foreign object detection status packet, whereinthe controller adjusts intensity of the wireless power based on adetermination result of whether the foreign object is present.

When the foreign object is not present as a determination result of thecontroller, guaranteed power may be maintained to second power asinitial setting, and when the foreign object is present as thedetermination result of the controller, the guaranteed power may bedownward-adjusted to first power from the second power.

The first power may be equal to or less than 5 W.

The controller may further determine whether the foreign object ispresent during charging with the adjusted intensity of the wirelesspower.

In one aspect, the controller may determine whether the foreign objectbased on the estimated power loss during charging, and as adetermination result of the power loss, when the foreign object ispresent, the controller may stop the power transmission for charging.

The wireless power transmitter may further include a sensor configuredto transmit information on intensity of the transmission power to thecontroller, wherein the controller may estimate power loss based oninformation on the intensity of transmission power during charging andinformation on the intensity of reception power received from thewireless power receiver to correspond to the transmission power and maycompare the estimated power loss with a preset power loss referencevalue to determine whether the foreign object is present.

In another aspect, the wireless power transmitter may further include asensor configured to transmit information on the measured information tothe controller, wherein the controller determines whether the foreignobject is present based on the calculated temperature change using themeasured temperature during charging, and as a determination resultbased on the temperature change, when the foreign object is present, thecontroller may stop power transmission for charging.

In another aspect, the controller may determine whether the foreignobject is present based on the estimated power loss during charging,when the foreign object is present as a determination result based onthe power loss, when the foreign object is present, the controller maydetermine whether the foreign object is present based on the measuredtemperature change during charging, and as a determination result basedon the temperature change, when the foreign object is present, thecontroller may stop power transmission for charging within apredetermined time period.

As the additional determination result, when the foreign object is notpresent, the controller may renegotiate a power transfer contract withthe corresponding wireless power receiver to reset guaranteed power.

The controller may transmit a response indicating that the foreignobject is present according to a determination result of whether theforeign object is present, and when currently set guaranteed power isgreater than first power, the controller may downward-adjust intensityof power to the first power or less.

In another embodiment, a computer readable recording medium havingrecorded thereon a program for executing the methods of wirelesscontrolling power transmission may be provided.

It is to be understood that both the foregoing general description andthe following detailed description of embodiments of the disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Arrangements and embodiments may be described in detail with referenceto the following drawings in which like reference numerals refer to likeelements and wherein:

FIG. 1 is a block diagram for explanation of a wireless charging systemaccording to an embodiment;

FIG. 2 is a block diagram for explanation of a wireless charging systemaccording to another embodiment;

FIG. 3 is a diagram for explanation of a produce of transmitting adetection signal in a wireless charging system according to anembodiment;

FIG. 4 is a state transition diagram for explanation of a wireless powertransmission procedure according to an embodiment;

FIG. 5 is a flowchart for explanation of a foreign object detectionprocedure in a wireless power transmission system according to anembodiment;

FIG. 6 is a block diagram for explanation of the structure of a wirelesspower transmission apparatus according to an embodiment;

FIG. 7 is a diagram for explanation of the configuration of thetransmission antenna of FIG. 6 according to an embodiment;

FIG. 8 is a block diagram illustrating the structure of a wireless powertransmission apparatus that is operatively associated with the wirelesspower transmission apparatus of FIG. 6 according to an embodiment;

FIG. 9 is a diagram for explanation of a method of controlling powertransmission according to whether a foreign object is detected by aconventional wireless power transmitter;

FIG. 10 is a diagram for explanation of a packet according to anembodiment;

FIG. 11 is a flowchart for explanation of a method of controlling powertransmission in a wireless power transmitter according to an embodiment;

FIG. 12 is a flowchart for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment;

FIG. 13 is a diagram for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment;

FIG. 14 is a diagram for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment;

FIG. 15 is a diagram for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment;

FIG. 16A is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter and a receiver have the same version;

FIG. 16B is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter and a receiver have different versions;

FIG. 16C is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter and a receiver have the same version; and

FIG. 16D is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter has a higher-ranking version than a receiver.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thedisclosure, examples of which are illustrated in the accompanyingdrawings. The suffixes “module” and “unit” of elements herein are usedfor convenience of description and thus may be used interchangeably anddo not have any distinguishable meanings or functions.

In description of exemplary embodiments, the suffixes “module” and“unit” of elements herein are embodied as a hardware element, forexample, a circuit device, a microprocessor, a memory, and a sensor, butthis is merely an embodiment and a partial or entire function of thecorresponding element may be embodied in the form of software.

In description of exemplary embodiments, it will be understood that,when an element is referred to as being “on” or “under” another element,the element can be directly on another element or intervening elementsmay be present. In addition, when an element is referred to as being“on” or “under” another element, this may include the meaning of anupward direction or a downward direction based on one component.

In the following description of the embodiments, for convenience ofdescription, an apparatus for wirelessly transmitting power in awireless power transmission system may be used interchangeably with awireless power transmitter, a wireless power transmission apparatus, atransmission end, a transmitter, a transmission apparatus, atransmission side, etc. In addition, for convenience of description, anapparatus having a function of wirelessly receiving power from awireless power transmission apparatus may be used interchangeably with awireless power reception apparatus, a wireless power receiver, areception terminal, a reception side, a reception apparatus, a receiver,etc.

A transmitter according to the disclosure may be configured in the formof a pad, a cradle, an access point (AP), a small base station, a stand,a ceiling insert type, a wall-hanging type, or the like, and onetransmitter may simultaneously transmit power to a plurality of wirelesspower reception apparatuses. To this end, a transmitter may include atleast one wireless power transmission element.

Here, a wireless power transmission element may use various wirelesspower transmission standards based on an electromagnetic inductionmethod of charging according to the electromagnetic induction principlethat a magnetic field is generated from a coil of a power transmissionend and electricity is induced from a coil of a reception end under theinfluence of the magnetic field. For example, the wireless powertransmission standards may include wireless charging technology of anelectromagnetic induction method defined in wireless power consortium(WPC) Qi and power matters alliance (PMA).

In addition, a wireless power receiver according to an embodiment mayinclude at least one wireless power reception element and may wirelesslyreceive power from one or more transmitter.

In addition, a receiver according to the disclosure may be mounted on asmall-size electronic apparatus such as a mobile phone, a smartphone, alaptop, a digital broadcasting terminal, a personal digital assistants(PDA), a portable multimedia player (PMP), a navigation system, an MP3player, an electric toothbrush, a radio frequency identification (RFID)tag, an illumination apparatus, a remote controller, a bobber, and asmart watch without being limited thereto. Accordingly, the receiver maybe any device as long as the receiver includes the wireless powerreception element according to the disclosure to charge a battery.

FIG. 1 is a block diagram for explanation of a wireless charging systemaccording to an embodiment.

Referring to FIG. 1, the wireless charging system may broadly include awireless power transmission end 10 configured to wirelessly transmitpower, a wireless power reception end 20 configured to receive thetransmission power, and an electronic device 30 configured to receivethe received power.

For example, the wireless power transmission end 10 and the wirelesspower reception end 20 may perform in-band communication of exchanginginformation using the same frequency band as an operation frequency usedin wireless power transmission.

In the in-band communication, upon receiving a power signal 41transmitted from the wireless power transmission end 10, the wirelesspower reception end 20 may modulate the received power signal and maytransmit the modulated signal 42 to the wireless power transmission end10.

In another example, the wireless power transmission end 10 and thewireless power reception end 20 may also perform out-of-bandcommunication of exchanging information using separate frequency bandsdifferent from an operation frequency used in wireless powertransmission.

For example, information exchanged between the wireless powertransmission end 10 and the wireless power reception end 20 may includecontrol information as well as state information of each other.

Here, the state information and the control information that areexchanged between transmission and reception ends will be obviouslyunderstood with reference to a description of the following embodiments.

The in-band communication and the out-of-band communication may providebi-directional communication without being limited thereto. According toanother embodiment, unidirectional communication or half-duplexcommunication may also be provided.

For example, in the unidirectional communication, the wireless powerreception end 20 may transmit information only to the wireless powertransmission end 10 without being limited thereto, and the wirelesspower transmission end 10 may also transmit information only to thewireless power reception end 20.

In the half-duplex communication, bi-directional communication may beenabled between the wireless power reception end 20 and the wirelesspower transmission end 10, but it may be possible to transmitinformation by only one device at any one time point.

The wireless power reception end 20 according to an embodiment mayacquire various pieces of state information of the electronic device 30.

For example, the state information of the electronic device 30 mayinclude current power usage information, information for identifyingexecuted application, CPU usage information, battery charging stateinformation, battery output voltage/current information, and the like,without being limited thereto, and may include any information that iscapable of being acquired from the electronic device 30 and being usedin wireless power control.

In particular, the wireless power transmission end 10 according to anembodiment may transmit a predetermined packet indicating whetherhigh-speed charging is supported, to the wireless power reception end20.

Upon checking that the wireless power transmission end 10 connected tothe wireless power reception end 20 supports a high-speed charging mode,the wireless power reception end 20 may notify the electronic device 30about this.

The electronic device 30 may display information indicating thathigh-speed charging is possible through a predetermined display deviceincluded therein—e.g., a liquid crystal display (LCD) device —.

FIG. 2 is a block diagram for explanation of a wireless charging systemaccording to another embodiment.

For example, as shown in a reference numeral 200 a, the wireless powerreception end 20 may include a plurality of wireless power receptionapparatuses, and the plurality of wireless power reception apparatusesmay be connected to one wireless power transmission end 10 to performwireless charging.

In this case, the wireless power transmission end 10 may distribute andtransmit power to the plurality of wireless power reception apparatusesusing a time-division method without being limited thereto, and inanother example, the wireless power transmission end 10 may distributeand transmit power to a plurality of wireless power receptionapparatuses using different frequency bands allocated to respectivewireless power reception apparatuses.

In this case, the number of wireless power reception apparatusesconnectable to one wireless power transmission end 10 may be adaptivelydetermined based on at least one of requested electric energy forrespective wireless power reception apparatuses, a battery chargingstate, power consumption of an electronic device, or available electricenergy of a wireless power transmission apparatus.

In another example, as shown in a reference numeral 200 b, the wirelesspower transmission end 10 may include a plurality of wireless powertransmission apparatuses.

In this case, the wireless power reception end 20 may be simultaneouslybe connected to the plurality of wireless power transmissionapparatuses, and may simultaneously receive power from the connectedwireless power transmission apparatuses to perform charging.

In this case, the number of wireless power transmission apparatusesconnected to the wireless power reception end 20 may be adaptivelydetermined based on requested electric energy of the wireless powerreception end 20, a battery charging state, power consumption of anelectronic device, available electric energy of a wireless powertransmission device, and the like.

FIG. 3 is a diagram for explanation of a produce of transmitting adetection signal in a wireless charging system according to anembodiment.

For example, three transmission coils 111, 112, and 113 may be installedin a wireless power transmitter. A partial region of each transmissioncoil may overlap another transmission coil, and a wireless powertransmitter may sequentially transmit predetermined detection signals117 and 127—for example, a digital ping signal—for detection of presenceof a wireless power receiver through each transmission coil in apredefined order.

As shown in FIG. 3, the wireless power transmitter may sequentiallytransmit the detection signal 117 through a primary detection signaltransmission procedure indicated by a reference numeral 110 and mayidentify the transmission coils 111 and 112 through which a signalstrength indicator 116 is received from a wireless power receiver 115.

Then, the wireless power transmitter may sequentially transmit thedetection signal 127 through a secondary detection signal transmissionprocedure indicated by a reference numeral 120, may identify atransmission coil with high power transmission efficiency (ortransmission efficiency)—that is, an alignment state between atransmission coil and a reception coil—among the transmission coils 111and 112 through which a signal strength indicator 126 is received, andmay perform control to transmit power—that is, to perform wirelesscharging—through the identified transmission coil.

As shown in FIG. 3, the wireless power transmitter performs thedetection signal transmission procedure twice in order to moreaccurately identify whether reception coils of the wireless powerreceiver are appropriately aligned in a transmission coil.

As shown in reference numerals 110 and 120 of FIG. 3, when a firsttransmission coil 111 and a second transmission coil 112 receive thesignal strength indicators 116 and 126, the wireless power transmittermay select a transmission coil that is the most appropriately alignedbased on the signal strength indicator 126 received by each of the firsttransmission coil 111 and the second transmission coil 112 and mayperform wireless charging using the selected transmission coil.

FIG. 4 is a state transition diagram for explanation of a wireless powertransmission procedure according to an embodiment.

Referring to FIG. 4, power transmission to a receiver from a transmitteraccording to an embodiment may be broadly classified into a selectionphase 410, a ping phase 420, an identification and configuration phase430, a negotiation phase 440, a calibration phase 450, a power transferphase 460, and a renegotiation phase 470.

The selection phase 410 may be a phase including—for example, S402,S404, S408, S410, and S412—which transitions when a specific error or aspecific event is detected while power transmissions is started or powertransmission is maintained.

Here, the specific error and the specific event would be obvious fromthe following description.

In addition, in the selection phase 410, the transmitter may monitorwhether an object is present on an interface surface.

Upon detecting that the object is present on the interface surface, thetransmitter may transition to the ping phase 420 (S403).

For example, in the selection phase 410, the transmitter may transmit ananalog ping signal with a very short pulse and may detect whether anobject is present in an active area of the interface surface based on acurrent change of a transmission coil (or a primary coil). Here, theactive area may refer to an area in which a receiver is disposed toenable wireless charging.

In another example, in the selection phase 410, the transmitter maydetect whether an object is present in an active area of an interfacesurface using a configured sensor.

For example, the sensor may include a hall sensor, a pressure sensor, acapacity sensor, a current sensor, a voltage sensor, a light detectionsensor, and the like, and thereamong, the sensor may detect an objectpresent in an active area through at least one sensor.

In the selection phase 410, upon detecting an object, the wireless powertransmitter may measure a quality factor corresponding to a configuredLC resonance circuit—for example, an LC resonant circuit including acoil (inductor) and a resonant capacitor that are connected in series toeach other —.

Upon detecting an object in the selection phase 410, the transmitteraccording to an embodiment may measure a quality factor value in orderto determine whether a wireless power receiver along with a foreignobject (FO) is present in a charging area.

Here, the quality factor value may be measured prior to entrance intothe ping phase 420. The quality factor value may be measured in thestate in which power transmission through a transmission coil istemporally stopped.

For example, the quality factor value may be measured with respect to apredefined reference operation frequency.

In another example, the quality factor value may also be measured viasampling in units of predetermined frequencies in an operation frequencyband used in wireless power transmission.

The transmitter according to an embodiment may check a frequency valuecorresponding to a quality factor value with a maximum value amongquality factor values measured in the same frequency hand and may storethe frequency value in a memory. Hereinafter, for convenience ofdescription, a frequency at which a quality factor value in the sameoperation frequency band is highest is referred to as a quality factorpeak frequency or is simply referred to as a peak frequency forconvenience of description.

Distribution of the quality factor value measured to correspond to theoperation frequency band and the quality factor peak frequency may bedifferent depending on a type of a wireless power transmitter.

In particular, a quality factor value measured using atransmitter—hereinafter, a ‘transmitter for authentication’ forconvenience of description—and an LCR meter used to authenticate areceiver with respect to the same operation frequency may be differentfrom a quality factor value measured by a commercially availabletransmitter.

Upon receiving a signal strength packet, the wireless power transmittermay enter the identification and configuration phase 430 (S403).

When the identification and configuration phase is normally completed,the wireless power transmitter may enter the negotiation phase 440(S405).

When the identification and configuration phase is normally completed,the wireless power transmitter may also enter the power transfer phase460 depending on a type of a receiver (S406).

When the wireless power transmitter enters the negotiation phase 440,the wireless power transmitter may receive an FOD status packetincluding a reference quality factor value from the wireless powerreceiver.

The wireless power transmitter may determine a quality factor thresholdvalue based on the received reference quality factor value.

Then, the wireless power transmitter may compare the measured qualityfactor value and the quality factor threshold value to determine whethera foreign object is present.

However, when a foreign object detection method of simply comparing apredetermined quality factor threshold value determined based on thereference quality factor value and a measured quality factor value todetect whether a foreign object is present is applied to a commerciallyavailable transmitter, the accuracy of detecting a foreign object may belowered.

Here, the reference quality factor value may refer to a quality factorvalue at a reference operation frequency measured in the state in whicha foreign object is not present in a charging region of a transmitterfor authentication.

The reference quality factor value received by the negotiation phase 440and a quality factor value hereinafter, a ‘current quality factor’ forconvenience of description—corresponding to a reference operationfrequency measured prior to the ping phase 420 may be compared with eachother to determine whether a foreign object is present.

However, a transmitter that measures the reference quality factorvalue—i.e., a transmitter for authentication—and a transmitter thatmeasures the current quality factor value may be different from eachother. Accordingly, the quality factor threshold value determined todetermine whether a foreign object is present may not be accurate.

Accordingly, the transmitter according to an embodiment may receive areference quality factor value corresponding to a type of thecorresponding transmitter from a wireless power receiver and may alsodetermine the quality factor threshold value based on the receivedreference quality factor value.

A transmission coil may have the inductance and/or series resistancecomponent in the transmission coil which may decrease due toenvironmental change, thereby changing (shifting) the resonant frequencyof the corresponding transmission coil. That is, a quality factor peakfrequency as a frequency at which the maximum quality factor value ismeasured in the operating frequency band may be shifted

For example, since the wireless power receiver includes a magneticshield (shielding material) having high permeability, the highpermeability may increase the inductance value measured in thetransmission coil. In contrast, a foreign object, which is a metallicmaterial, decreases the inductance value.

Generally, in the case of an LC resonant circuit, the resonant frequencyf_resonant is calculated by

$\frac{1}{2\pi \sqrt{LC}}.$

When only the wireless power receiver is placed in the charging area ofthe transmitter, the L value increases, and thus the resonant frequencydecreases. That is, the resonant frequency is moved (shifted) to theleft on the frequency axis.

In contrast, when a foreign object is placed in the charging area of thetransmitter, the L value decreases, and thus the resonant frequencyincreases. That is, the resonant frequency is moved (shifted) to theright on the frequency axis.

The transmitter according to another embodiment may determine whetherthe foreign object placed in the charging area is present based on achange in the quality factor peak frequency.

The transmitter may acquire information on a preset quality factor peakfrequency—hereinafter, a ‘reference quality factor peak frequencypf_reference’ or ‘reference peak frequency’ for convenience ofdescription corresponding to the corresponding transmitter type from thereceiver or may maintain the information in a predetermined recordingregion.

Upon detecting that an objecting is placed in the charging area, thetransmitter may measure a quality factor value in the operationfrequency band prior to entrance into the ping phase 420 and mayidentify the quality factor peak frequency based on the measured result.Here, in order to distinguish the identified quality factor peakfrequency from the reference quality factor peak frequency, the qualityfactor peak frequency may be referred to as a ‘measured quality factorpeak frequency pf_measured’ or ‘measured peak frequency’.

In the negotiation phase 440, the transmitter may determine whether theforeign object is present based on the reference quality factor peakfrequency and the measured quality factor peak frequency.

When information on the reference quality factor peak frequency isreceived from the receiver, the information may be received through apredetermined packet in the identification and configuration phase 430or the negotiation phase 440.

For example, the transmitter may transmit information on thetransmission type thereof to the receiver in the identification andconfiguration phase 430. The receiver may read a pre-stored referencequality factor peak frequency corresponding to the received transmittertype information from a corresponding memory and may transmitinformation on the read reference quality factor peak frequency to thetransmitter.

The transmitter according to another embodiment may determine whetherthe foreign object is present using both a foreign object detectionmethod based on the quality factor peak frequency and a foreign objectdetection method based on the quality factor value. For example, If adifference between the reference quality factor value corresponding to atransmitter type and the measured quality factor is small, for example,if the difference is equal to or less than 10%, presence of the foreignobject may be determined by comparing the reference peak frequencycorresponding to the transmitter type with the measured quality factorpeak frequency. In contrast, if the difference between the two qualityfactor values is greater than 10%, the transmitter may immediatelydetermine that the foreign object is present.

According to another embodiment, upon determining that the qualityfactor threshold value determined based on the reference quality factorvalue corresponding to the transmitter type with the measured qualityfactor, the transmitter may also compare the reference quality factorpeak frequency corresponding to the transmitter type with the measuredquality factor peak frequency to determine whether the foreign object ispresent.

If it is difficult to detect the foreign object using the quality factorvalue, the transmitter may make a request to the identified receiver forinformation on the reference quality factor peak frequency correspondingto the corresponding transmitter type. Then, upon receiving informationon the reference quality factor peak frequency from the receiver, thetransmitter may determine whether the foreign object is present usingthe reference quality factor peak frequency and the measured qualityfactor peak frequency. As such, the transmitter may more accuratelydetect the foreign object placed in the charging area.

When the object is detected, the transmitter may enter the ping phase420, may wake up the receiver, and may transmit a digital ping foridentifying whether the detected object is a wireless power receiver.

In the ping phase 420, when a response signal to the digital ping, forexample, a signal strength packet s not received from the receiver, thetransmitter may transition to the selection phase 410 again.

In the ping phase 420, when a signal indicating that power transfer hasbeen completed, that is, an end charging packet, is received from thereceiver, the transmitter may transition to the selection phase 410.

When the ping phase 420 is completed, the transmitter may transition tothe identification and configuration phase 430 for identifying thereceiver and collecting the configuration and status information of thereceiver.

In the identification and configuration phase 430, the transmitter mayalso transmit information on a transmitter type to the receiver.

In the identification and configuration phase 430, the receiver may makea request to the transmitter for information on the transmitter type,and the transmitter may also transmit the information on the transmittertype to the receiver according to the request of the receiver.

In the identification and configuration phase 430, when an unexpectedpacket is received, when an expected packet is not received during apredetermined time (timeout), when a packet transmission error occurs,or when power transfer contract is not established (no power transfercontract), the transmitter may transition to the selection phase 410.

The transmitter may determine whether entry into the negotiation phase440 is necessary based on the negotiation field value of theconfiguration packet received in the identification and configurationphase 430.

As the check result, when negotiation is required, the transmitter mayenter the negotiation phase 440 to perform a predetermined FODprocedure.

In contrast, as the check result, when negotiation is not required, thetransmitter may immediately transition to the power transfer phase 460.

Upon checking that the corresponding wireless power receiver in theidentification and configuration phase 430 is a receiver supporting onlya first power transmission mode, the wireless power transmitteraccording to an embodiment may not perform the negotiation phase 440 andmay immediately enter the power transfer phase 460.

The wireless power transmitter may enter the power transfer phase 460and then may periodically perform a predetermined foreign objectdetection procedure.

The foreign object detection procedure may be a foreign object detectionprocedure based on the quality factor value without being limitedthereto, and a foreign object detection procedure based on power lossmay be applied.

A foreign object detection procedure based on power loss is a method ofcomparing a difference between transmission power of the wireless powertransmitter and reception power of the wireless power receiver with apredetermined reference to determine whether the foreign object ispresent and a detailed procedure will be more obvious with reference tothe following description of the drawings.

For example, in the negotiation phase 440, the transmitter may receive aFOD status packet including a reference quality factor value. Inaddition, the transmitter may receive the FOD status packet including areference peak frequency value corresponding to the transmitter type.

In another example, in the negotiation phase 440, the transmitter mayalso receive a status packet including a reference quality factor valuecorresponding to the transmitter type and the reference peak frequencyvalue. In this case, the transmitter may determine a quality factorthreshold value for foreign object detection based on the referencequality factor value corresponding to the transmitter type.

The transmitter may also determine a quality factor peak frequencythreshold value for foreign object detection based on the referencequality factor peak frequency value corresponding to the transmittertype.

The transmitter may compare the determined quality factor thresholdvalue and(or) the determined quality factor peak frequency thresholdvalue with the measured quality factor value—which indicates a qualityfactor value measured prior to the ping phase 420—and(or) a measuredquality factor peak frequency value to detect a foreign object placed inthe charging area.

The transmitter may control power transmission according to the foreignobject detection result. For example, when the foreign object isdetected, the transmitter may transmit a negative acknowledge packet(NACK) to the receiver in response to the FOD status packet.Accordingly, power transmission may be stopped without being limitedthereto.

The transmitter may compare the determined quality factor peak frequencythreshold value and the measured quality factor peak frequency value todetect the foreign object placed in the charging area. The transmittermay control power transmission according to the foreign object detectionresult. For example, when the foreign object is detected, thetransmitter may transmit a negative acknowledge packet (NACK) to thereceiver in response to a FOD status packet. Accordingly, powertransmission may be stopped without being limited thereto.

When the foreign object is detected, the transmitter may receive an endof charge message from the receiver and may enter the selection phase410 based on the end of charge message.

When the foreign object is detected in the negotiation phase 440, thetransmitter according to another embodiment may enter the power transferphase 460 (S415).

In contrast, when the foreign object is not detected, the transmittermay complete the negotiation phase 440 with respect to transmissionpower and may enter the power transfer phase 460 through the calibrationphase 450 (S407 and S409).

In detail, when the foreign object is not detected, if the transmitterenters the calibration phase 450, the transmitter may determine thestrength of the power received by a reception end and may measure powerloss between a transmission end and a reception end in order todetermine the intensity of power to be transmitted from the transmissionend.

For example, the transmitter may determine reception power intensity ofthe receiver based on reception power intensity information fed backfrom the reception end during power transmission. That is, thetransmitter may predict (or calculate) based on an intensity differencebetween transmission power at a transmission end and reception power ata reception end in the calibration phase 450.

In the power transfer phase 460, when an unexpected packet is received,when an expected packet is not received during a predetermined time(timeout), when predetermined power transfer contract violation occurs,or when charging is completed, the transmitter may transition to theselection phase 410 (S410).

In addition, in the power transfer phase 460, when the power transfercontract needs to be reconfigured according to transmitter state change,the transmitter may transition to the renegotiation phase 470 (S411). Inthis case, when renegotiation is normally completed, the transmitter mayreturn to the power transfer phase 460 (S413).

The power transfer contract may be configured based on the transmitterand receiver status information and characteristic information. Forexample, the transmitter status information may include information onthe maximum amount of transmittable power, information on the maximumnumber of receivable receivers, etc. and the receiver status informationmay include information on required power.

The wireless power transmitter according to an embodiment may beoperated based on any one of a first power transfer mode and a secondpower transfer mode based on guaranteed power requested by the wirelesspower receiver.

The wireless power transmitter according to another embodiment may beoperated based on any one of the first power transfer mode and thesecond power transfer mode based on the determination result aboutwhether the foreign object is present.

The wireless power receiver connected to the wireless power transmittermay be a receiver that supports only the first power transfer mode or areceiver that supports both the first power transfer mode and the secondpower transfer mode.

Here, guaranteed power to be set in the second power transfer mode maybe greater than guaranteed power to be set in the first power transfermode.

For example, the guaranteed power to be set in the first power transfermode may be first power—for example, 5 W or less—and the guaranteedpower to be set in the second power transfer mode may be greater thanthe first power and may be less than second power—for example, 15 W—.

FIG. 5 is a flowchart for explanation of a foreign object detectionprocedure in a wireless power transmission system according to anembodiment.

In detail, FIG. 5 is a diagram for explanation of a foreign objectdetection procedure in a second power transfer mode.

Referring to FIG. 5, when an object is detected in a selection phase, awireless power transmitter 510 may measure a quality factor value at apredetermined reference operation frequency prior to entrance to a pingphase (S501). Here, the reference operation frequency may be a resonantfrequency without being limited thereto. The wireless power transmitter510 may store the measured quality factor value in an internal memory(S502).

The wireless power transmitter 510 may enter a ping phase and mayperform the detection signal transmission procedure described above withreference to FIG. 3 (S503).

When a wireless power receiver 520 is detected, the wireless powertransmitter 510 may enter an identification and configuration phase toreceive an identification packet and a configuration packet (S504 andS505).

The wireless power transmitter 510 may enter a negotiation phase and mayreceive a FOD status packet from the wireless power receiver 520 (S506).Here, the FOD status packet may include a reference quality factorvalue.

The wireless power transmitter 510 may determine a threshold value fordetermining whether the foreign object is present based on the referencequality factor value included in the FOD status packet (S507).

For example, the threshold value may be determined as a value that isless than the reference quality factor value by a predetermined ratio.

The wireless power transmitter 510 may compare the measured qualityfactor value with the determined threshold value to detect a foreignobject (S508). Here, when the measured quality factor value is less thanthe threshold value, the wireless power transmitter 510 may determinethat the foreign object is present in the charging area.

The wireless power transmitter 510 may transmit an ACK response, a NACKresponse, or a no decision (ND) response to the wireless power receiver520 according to the detection result of the foreign object (S509).

When the wireless power receiver 520 receives the NACK response or theND response from the wireless power transmitter 510, the wireless powerreceiver 520 may be controlled not to supply power with predeterminedintensity or greater to an electronic device (or a battery/load) throughan output terminal thereof until power transmission by the wirelesspower transmitter 510 is completely stopped.

Here, the power with predetermined intensity or greater may be 5 W as areference without being limited thereto, and may be differently definedaccording to a design of one of ordinary skill in the art and anelectronic device having the wireless power receiver 520 installedtherein (or a battery/load connected to the wireless power receiver520).

FIG. 6 is a block diagram for explanation of the structure of a wirelesspower transmission apparatus according to an embodiment.

Referring to FIG. 6, a wireless power transmission apparatus 600 mayinclude a controller 610, a gate driver 620, an inverter 630, atransmission antenna 640, a power source 650, a power supply 660, asensor 670, and a demodulator 680.

The power supply 660 may convert DC current or AC current applied fromthe power source 650 and may provide the same to the inverter 630.Hereinafter, for convenience of description, a voltage supplied to theinverter 630 from the power supply 660 will be referred to as aninverter input voltage or V_rail.

The power supply 660 may include at least one of an AC/DC converter or aDC/DC converter depending on a type of power applied from the powersource 650.

For example, the power supply 660 may be a switching mode power supply(SMPS) and may use a switching control method of converting AC powerinto DC power using a switching transistor, a filter, a rectifier, andthe like. Here, the rectifier and the filter may be independentlyconfigured and may be placed between the AC power source and the SMPS.

The SMPS may be a power supply that controls an on/off time ratio of asemiconductor switch device to supply DC power with stabilized output toa corresponding device or a circuit device and is capable of having highefficiency, being miniaturized, and being lightweight, and thus has beenwidely used in most of electronic devices and equipment.

The stability and precision of an electronic circuit operation may bemostly dependent upon the quality of a power source. In general, amethod of converting stable power from a battery and commerciallyavailable AC power and supplying the power may be broadly classifiedinto a series regulator method and a switched mode method.

The series regulator method used in a TV set, a CRT monitor, or the likehas simple and inexpensive surrounding circuits but the circuitsdisadvantageously generate a large amount of heat, have low powerefficiency, and have a large volume.

In contrast, the switched mode method is advantageous that heat isbarely generated, power efficiency is high, and a circuit volume issmall, but is disadvantageous that circuits are expensive and complexand interfere with output noise in terms of electromagnetic waves due tohigh-frequency switching.

In another example, the power supply 660 may be a variable switchingmode power supply (SMPS). The variable SMPS may switch and rectify an ACvoltage in a band of a several tens of Hz output from an AC power supplyto generate a DC voltage.

The variable SMPS may output a DC voltage in a predetermined level ormay also adjust an output level of the DC voltage according topredetermined control of a Tx controller. The variable SMPS may controla supply voltage according to an output power level of a poweramplifier—that is, the inverter 630—and may maintain maximum efficiencyin all output levels to allow a power amplifier of the wireless powertransmitter to always operate in a saturated region with highefficiency.

When a commercially available SMPS that is generally used is usedinstead of the variable SMPS, the variable DC/DC converter may beadditionally used. The commercially available SMPS and the variableDC/DC converter may control a supply voltage according to an outputpower level of a power amplifier and may maintain the maximum efficiencyin all output levels to ally the power amplifier to operate in asaturated region with high efficiency. According to an embodiment, thepower amplifier may use a Class E type without being limited thereto.

The inverter 630 may convert a DC voltage V_rail in a predeterminedlevel into an AC voltage to generate AC power to be wirelesslytransmitted, according to a switching pulse signal—that is, a pulsewidth modulated signal—in a band of several MHz to several tens of MHz,received through the gate driver 620.

In this case, the gate driver 620 may generate a plurality of PWMsignals SC_0 to SC_N for control of a plurality of switches included inthe inverter 630 using a reference clock Ref_CLK signal supplied fromthe controller 610.

Here, when the inverter 630 includes a half bridge circuit, N may be 1,and when the inverter 630 includes a full bridge circuit, N may be 3,without being limited thereto, and different numbers of PWM signals foreach inverter type may be supplied depending on a design type of theinverter 630.

For example, in the embodiment of FIG. 6, when the inverter 630 includesa full bridge circuit including four switches, the inverter 630 mayreceive four PWM signals SC_0, SC_1, SC_2, and SC_3 for control of therespective switches from the gate driver 620.

In contrast, in the embodiment of FIG. 6, when the inverter 630 includesa half bridge circuit including two switches, the inverter 630 mayreceive second PWM signals SC_0 and SC_1 for control of the respectiveswitches from the gate driver 620.

The transmission antenna 640 may include at least one power transmissionantenna (not shown)—for example, an LC resonant circuit—for wirelesslytransmitting an AC power signal received from the inverter 630 and amatching circuit (not shown) for impedance matching.

When the transmission antenna 640 includes a plurality of transmissioncoils, the transmission antenna 640 may further include a coil selectioncircuit (not shown) for selection of a transmission coil to be used inwireless power transmission among a plurality of transmission coils.

The sensor 670 may include various sensing circuits for measuringintensity of the power/voltage/current input from the inverter 630 or(and) intensity of the power/power/voltage/current flowing in atransmission coil included in the transmission antenna 640, temperatureand temperature change in a specific position inside the wireless powertransmitter—e.g., which includes a transmission coil, a charging bed, acontrol circuit board, or the like —, and the like. Here, informationsensed by the sensor 670 may be transmitted to the controller 610.

The sensor 670 may measure intensity of current flowing in thetransmission coil while an analog ping is transmitted in the selectionphases 410 and 510 and may transmit the intensity of current to thecontroller 610. The controller 610 may compare intensity information ofcurrent flowing in the transmission coil in the selection phase with apredetermined reference to detect whether an object placed in thecharging area is present.

When the wireless power transmitter 600 performs in-band communicationwith the wireless power receiver, the wireless power transmitter 600 mayinclude the demodulator 680 connected to the transmission antenna 640.

The demodulator 680 may demodulate an amplitude-modulated in-band andmay transmit the signal to the controller 610.

For example, the controller 610 may check whether a signal strengthindicator corresponding to a transmitted digital ping is received, basedon the demodulated signal received from the demodulator 680.

Upon detecting an object placed in the charging area in the selectionphase 410, the controller 610 may enter the ping phase 420 and mayperform control to transmit a digital ping through the transmissionantenna 640.

Upon detecting the object placed in the charging area in the selectionphase 410, the controller 610 may temporally stop power transmission andmay measure a quality factor value prior to entrance into the pingphase. Here, the measured quality factor value may be maintained in apredetermined memory (not shown) included in the wireless powertransmitter 600.

Upon checking that the signal strength indicator is received in the pingphase, the controller 610 may stop transmitting the digital ping and mayenter the identification and configuration phase 430 to receive theidentification packet and the configuration packet.

Upon receiving an end power transfer packet after entrance into thepower transfer phase 460, the controller 610 may stop power transmissionand may enter the selection phase 410.

When the foreign object is present in the charging area, the controller610 may stop power transmission and may enter the selection phase 410.

According to an embodiment, the controller 610 may calculate (orestimate) power loss on a wireless power transmission path based on thesignal strength packet received from the wireless power receiver. Thecontroller 610 may determine whether the foreign object is present basedon the calculated (or estimated) power loss.

According to another embodiment, the controller 610 may measure atemperature change based on temperature sensing information receivedfrom the sensor 670 or temperature measurement information received fromthe wireless power receiver. The controller 610 may also determinewhether the foreign object is present based on the measured temperaturechange.

According to another embodiment, the controller 610 may also perform aprocedure of estimating power loss and determining whether the foreignobject is present based on the temperature change according to adetermination result of whether the foreign object is present based onthe estimated power loss.

According to another embodiment, the controller 610 may also perform aprocedure of determining whether the foreign object is present based onpower loss according to determination result of whether the foreignobject is present based on a temperature change.

According to the disclosure, upon receiving an FOD status packet in thenegotiation phase 440, the controller 610 may determine a thresholdvalue for foreign object detection based on the received FOD statuspacket and may also determine whether the foreign object is presentbased on the determined threshold value.

Here, the FOD status packet may include at least one of a referencequality factor value, a resonant frequency, or a quality factor value atthe resonant frequency.

Upon receiving an end power transfer packet including a ripping code oran overheating code through the demodulator 680 in the power transferphase 460, the controller 610 may stop power transmission and may enterthe selection phase 410 to drive a ripping timer.

The controller 610 may suppress analog ping transmission and beep signaloutput until the driven ripping timer expires. Then, when the rippingtimer expires, the controller 610 may enter the ping phase 420 and mayperform control to transmit the digital ping through the transmissionantenna 640.

Upon receiving an end power transfer packet including the ripping codeor the overheating code after identification and configuration arecompleted on the detected receiver, the controller 610 may reset aripping time and then may return to the selection phase 410.

According to an embodiment, an operation mode of the wireless powertransmitter 600 may include a first power transfer mode and a secondpower transfer mode.

The controller 610 may be operated in any one of the first powertransfer mode and the second power transfer mode based on thedetermination result of whether the foreign object is present in thenegotiation phase 440.

Here, guaranteed power in the second power transfer mode may be greaterthan guaranteed power (or maximum transmission power) in the first powertransfer mode.

For example, the guaranteed power in the first power transfer mode maybe 5 W—hereinafter, referred to as first power—and the guaranteed powerin the second power transfer mode may be 15 W—hereinafter, referred toas second power —.

In another example, the guaranteed power in the first power transfermode may be 5 W and the guaranteed power in the second power transfermode may be a value between the first power and the second power withoutbeing limited thereto, and it may be noted that guaranteed powercorresponding to each operation mode is differently set according to adesign of one of ordinary skill in the art.

When the foreign object is present as the determination result ofwhether the foreign object is present in the negotiation phase 440, thecontroller 610 may change a level of the guaranteed power from a secondlevel corresponding to the second power transfer mode to a first levelcorresponding to the first power transfer mode.

That is, upon determining that the foreign object is present in thenegotiation phase 440, the controller 610 may downward-adjust theguaranteed power. As such, a device may be prevented from being damageddue to overheating by the foreign object during transmission of highpower.

Upon entering the first power transfer mode, the controller 610 mayperform control not to perform the calibration phase 450 of FIG. 4above.

Even if the foreign object is present in the charging area, when thecalibration phase 450 is performed in the first power transfer mode,there is a problem in that the accuracy of the foreign object detectionmethod based on power loss is lowered.

In general, the calibration phase 450 is a procedure performed assumingthat the foreign object is not present. Accordingly, even if the foreignobject is present in the charging area, when the calibration phase 450is performed, there is a problem in that the accuracy of the foreignobject detection method based on power loss is lowered, and thus themethod is not reliable.

After entrance into the first power transfer mode, when the foreignobject is not detected through the foreign object detection method basedon power loss and (or) the foreign object detection method based on atemperature change, the controller 610 may enter the renegotiation phase470 of FIG. 4.

When the power transfer contract is established according to therenegotiation with the wireless power receiver, the controller 610 mayalso change an operation mode according to the established powertransfer contract.

For example, the power transfer contract may include guaranteed power,and the controller 610 may change and set guaranteed power through therenegotiation procedure with the wireless power receiver.

According to the renegotiation result, when guaranteed power requestedby the wireless power receiver is changed to second guaranteed powercorresponding to the second power transfer mode from the firstguaranteed power corresponding to the first power transfer mode, thecontroller 610 may change the operation mode to the second powertransfer mode from the first power transfer mode.

As described in the above embodiment, even if a foreign object is notactually present, when the wireless power transmitter 600 according tothe disclosure determines that the foreign object is present, continuouscharging may be advantageously performed.

In detail, even if a foreign object is not actually present during aninitial operation in the second power transfer mode, when the wirelesspower transmitter 600 determines that the foreign object is present, thewireless power transmitter 600 may not immediately stop charging butinstead may change a power transmission mode to the first power transfermode from the second power transfer mode to maintain charging.

For example, even if the wireless power receiver is placed in thecharging area without a foreign object, the wireless power transmitter600 may determine that the foreign object according to an alignmentstatus between the transmission coil and the reception coil.

The wireless power transmitter 600 according to the disclosure may alsoperform an additional foreign object detection procedure after thechange to the first power transfer mode is performed, and thus it may beadvantageous that the foreign object may be more accurately detected.Here, the additional foreign object detection procedure may include atleast one of the foreign object detection procedure based on power lossor the foreign object detection procedure based on a temperature change.

FIG. 7 is a diagram for explanation of the configuration of thetransmission antenna of FIG. 6 according to an embodiment.

Referring to FIG. 7, the transmission antenna 640 may include a coilselection circuit 710, a coil assembly 720, and a resonant capacitor730.

The coil assembly 720 may include at least one transmission coil—thatis, first to N^(th) coils —.

The coil selection circuit 710 may include a switching circuitconfigured to transmit output current I_coil of the inverter 630 to anyone or at least one of transmission coils included in the coil assembly720.

For example, the coil selection circuit 710 may include first to N^(th)switches with one end connected to an output end of an inverter and theother end connected to a corresponding coil.

The first to N^(th) coils included in the coil assembly 720 may have oneend connected to a corresponding switch of the coil selection circuit710 and the other end connected to the resonant capacitor 730.

The demodulator 680 may demodulate a signal between the coil assembly720 and the resonant capacitor 730—here, the signal is anamplitude-modulated signal—and may transmit the demodulated signal tothe controller 610.

FIG. 8 is a block diagram illustrating the structure of a wireless powertransmission apparatus that is operatively associated with the wirelesspower transmission apparatus of FIG. 6 according to an embodiment.

Referring to FIG. 8, a wireless power receiver 800 may include areception antenna 810, a rectifier 820, a DC/DC converter 830, a switch840, a load 850, a sensing unit 860, a modulator 870, and a maincontroller 880.

The wireless power receiver 800 shown in the example of FIG. 8 mayexchange information with a wireless power transmitter via in-bandcommunication.

The reception antenna 810 may include an inductor and at least onecapacitor.

AC power transmit by the wireless power transmitter 600 may betransferred to the rectifier 820 through the reception antenna 810. Therectifier 820 may convert the AC power received through the receptionantenna 810 into DC power and may transmit the DC power to the DC/DCconverter 830.

The DC/DC converter 830 may convert the strength of the DC power outputfrom the rectifier 820 into a specific strength required by the load850.

The sensing unit 860 may measure the strength of the DC power outputfrom the rectifier 820 and may provide the measured result to the maincontroller 880.

The main controller 880 may perform power control based on the output DCpower of the rectifier 820.

The sensing unit 860 may measure the strength of current applied to thereception antenna 810 according to wireless power reception and maytransmit the measured result to the main controller 880.

In addition, the sensing unit 860 may measure the internal temperatureof the wireless power receiver 800 or an electronic device having thewireless power receiver 800 installed therein and may provide themeasured temperature value to the main controller 880.

For example, the main controller 880 may compare the strength of the DCpower output from the rectifier with a predetermined reference value anddetermine whether overvoltage occurs. As the determination result, upondetermining that overvoltage occurs, the main controller 880 maytransmit a predetermined packet indicating that overvoltage has occurredto the wireless power transmitter 600 through the modulator 870.

Upon receiving a packet from the main controller 880, the modulator 870may generate an amplitude modulate signal corresponding to the receivedpacket using AC power received through the reception antenna 810 and anincluded switch. In this case, the wireless power transmitter 600 maydemodulate the signal that is amplitude-modulated by the wireless powerreceiver 800, through the included demodulator 680.

For example, upon receiving the signal strength packet from the maincontroller 880 in the ping phase, the modulator 870 mayamplitude-modulate the digital ping received through the receptionantenna 810 according to the received signal strength packet.

The modulator 870 according to an embodiment may include a modulationswitch configured to amplitude-modulate the AC power signal receivedthrough the reception antenna 810. In this case, the main controller 880may transmit a pulse width modulation signal corresponding to atransmission target packet to the modulator 870 and may directly controlthe modulation switch.

When intensity of output DC power of the rectifier is equal to orgreater than a predetermined reference, the main controller 880 maydetermine that the detection signal—for example, a digital ping—isreceived, and upon receiving the detection signal, the main controller880 may control perform control to transmit the signal strength packetcorresponding to the corresponding detection signal to the wirelesspower transmitter through the modulator 870.

For example, when internal temperature is greater than a predeterminedreference, the main controller 880 may control the switch 840—forexample, switch OFF—not to transmit output DC power of the DC/DCconverter 830 to the load 850. In this case, the main controller 880 maytransmit a power transfer stop packet including the overheating code tothe wireless power transmitter 600 through the modulator 870.

In another example, the main controller 880 may be operativelyassociated with a power management device—for example, a powermanagement IC (PMIC)—configured to control internal power of anelectronic device having the wireless power receiver 800 installedtherein.

In this case, the output DC power of the DC/DC converter 830 may betransmitted to the power management device through the switch 840 andthe power management device may control battery charging and powersupply from an internal component of an electronic device.

The power management device may provide battery charging statusinformation to the main controller 880. The main controller 880 maydetermine whether charging is performed based on the battery chargingstatus information and internal temperature information.

When the wireless power receiver 800 according to an embodiment entersthe negotiation phase 440, the wireless power receiver 800 may generatethe FOD status packet and may transmit the same to the wireless powertransmitter 600.

For example, the FOD status packet may include a reference qualityfactor value.

In another example, a foreign object detection packet may include areference quality factor value and a resonant frequency corresponding tothe corresponding wireless power receiver.

In another example, the foreign object detection packet may include aresonant frequency and a quality factor corresponding to the resonantfrequency.

The wireless power transmitter 600 may determine a predeterminedthreshold value for determining whether the foreign object is presentbased on the reference quality factor value included in the FOD statuspacket.

The wireless power receiver 800 according to the above embodiment shownin FIG. 8 may further include a demodulator (not shown) configured todemodulate a packet transmitted by the wireless power transmitter 600.

As such, the wireless power transmitter 600 and the wireless powerreceiver 800 may perform bi-directional communication. According to anembodiment, bi-directional communication may be time-divisioncommunication in which the packet transmittable time in the wirelesspower transmitter and packet transmittable time in the wireless powerreceiver are distinguished from each other without being limitedthereto.

FIG. 9 is a diagram for explanation of a method of controlling powertransmission according to whether a foreign object is detected by aconventional wireless power transmitter.

Upon receiving a negotiation request packet from a wireless powerreceiver, the wireless power transmitter may transmit a grant packet toenter the negotiation phase 440.

Referring to FIG. 9, in the negotiation phase 440, the wireless powertransmitter may receive an FOD status packet from the wireless powerreceiver (S901).

For example, as shown in FIG. 10, the wireless power transmitter mayreceive the FOD status packet having a reference quality factor value1031 in the message 1030 field.

The wireless power transmitter may determine whether the foreign objectis present (S902). Here, the wireless power transmitter may detect anobject in the selection phase 410 and may then compare a quality factorvalue measured prior to entrance into the ping phase 420 and a qualityfactor threshold value determined based on the reference quality factorvalue received in the negotiation phase 440 to determine whether theforeign object is present.

In the following embodiment, a foreign object detection method will beexemplified as a foreign object detection method after entrance into thenegotiation phase 440, but this is merely an embodiment and it may benoted that different methods are applied as a foreign object detectionmethod in the negotiation phase according to a design of one of ordinaryskill in the art or standard definition.

As the determination result, when the foreign object is not present, thewireless power transmitter may transmit an ACK signal to thecorresponding wireless power receiver (S903).

Then, the wireless power transmitter may receive a guaranteed powerpacket including information on guaranteed power requested by thewireless power receiver (S904).

The wireless power transmitter may receive the end negotiation packetfrom the wireless power receiver (S905).

Upon receiving the end negotiation packet, the wireless powertransmitter may enter the calibration phase 450 from the negotiationphase 440.

The wireless power transmitter may enter the calibration phase 450 toperform a predetermined calibration procedure (S906).

When the power transfer contract is completed through the calibrationprocedure, the wireless power transmitter may enter the power transferphase 460 and may begin charging (S907).

As the determination result of operation 902, when the foreign object ispresent, the wireless power transmitter may transmit a NACK signal inresponse to the FOD status packet (S908).

Upon receiving the NACK signal in response to the FOD status packet, thewireless power receiver may perform control to prevent power at anoutput end thereof from exceeding a predetermined reference—for example,5 W without being limited until a power signal received from thewireless power transmitter is completely removed.

The wireless power transmitter may stop power transmission within apredefined time—for example, 5 seconds—after the NACK signal istransmitted (S909).

When power transmission is stopped, the wireless power transmitter mayenter the selection phase 410 (S910).

When power corresponding to the second power transfer mode istransmitted in the state in which the foreign object is placed in thecharging area, this may increase heating riskiness of a device.

Accordingly, upon determining that the foreign object is present, theconventional wireless power transmitter may block entrance into thepower transfer phase 460, may stop power transmission within apredefined time, and may then enter the selection phase 410.

However, even if a foreign object is not actually present, the wirelesspower transmitter may incorrectly determine that the foreign object ispresent because of measurement error of an LCR meter included in thewireless power transmitter, quality factor cross calibration error dueto a device design of the wireless power transmitter and the wirelesspower receiver and a design difference of coils installed therein, adistance between the transmission coil and the reception coil—that is, Zdistance—a position of the wireless power receiver placed in thecharging area—that is, XY displacement —, and the like.

Even if a foreign object is not actually present, when powertransmission is unconditionally stopped and then returns to theselection phase, a user may go through serious inconvenience.

In particular, a wireless power receiver applied to a smartphone or thelike may use a shielding material with high permeability in order toreduce the thickness of a corresponding product and may be designed tominimize the thickness of the reception coil.

In this case, resistance R may be remarkably increased and the qualityfactor Q may be remarkably reduced. When a housing formed of a metallicmaterial is applied to the corresponding product, the quality factor Qmay be further lowered.

This may increase error probability of determination of whether theforeign object is present in the wireless power transmitter.

For example, the case in which error of determination of whether theforeign object is present occurs may include a situation in which thequality factor Q is measured to be low and the foreign object isdetermined to be present even if a smartphone is placed in the chargingarea, a situation which a smartphone as well as the foreign object isplaced in the charging area, and the like.

Accordingly, there is a need for a method of controlling powertransmission for minimizing user convenience while preventing a devicefrom being damaged due to overheating in order to overcome the aboveconventional problem.

FIG. 10 is a diagram for explanation of a packet according to anembodiment.

The wireless power transmission end 10 and the wireless power receptionend 20 according to an embodiment may exchange a packet through in-bandcommunication, but this is merely one embodiment, and the correspondingpacket may also be exchanged through out-of-band communication.

Referring to FIG. 10, a packet format 1000 used for information exchangebetween the wireless power transmission end 10 and the wireless powerreception end 20 may include a preamble 1010 field for acquiringsynchronization for demodulation of the corresponding packet andidentifying an accurate start bit of the corresponding packet, a header1020 field for identifying the type of a message included in thecorresponding packet, a message 1030 field for transmitting the content(or payload) of the corresponding packet, and a checksum 1040 field foridentifying whether an error has occurred in the corresponding packet.

A packet reception end may identify the size of the message 1030included in the corresponding packet based on the value of the header1020.

A type of a packet to be transmitted for each operation of FIG. 4 abovemay be defined according to values of the header 1020, and some valuesof the header 1020 may be commonly defined in different operations of awireless power transmission procedure. For example, in the ping phase420 and the power transfer phase 460, an end power transfer packet forstopping power transmission of the wireless power transmitter may bedefined by the same header 1020.

The message 1030 includes data to be transmitted by the transmission endof the corresponding packet. For example, the data included in themessage 1030 field may be a report, a request, or a response, withoutbeing limited thereto.

The packet format 1000 according to another embodiment may furtherinclude at least one of transmission end identification information foridentifying the transmission end for transmitting the correspondingpacket or reception end identification information for identifying thereception end for receiving the corresponding packet.

Here, the transmission end identification information and the receptionend identification information may include IP address information,medium access control (MAC) address information, product identificationinformation, etc. However, the present disclosure is not limited theretoand information for distinguishing the reception end and thetransmission end in the wireless charging system may be included.

The packet format 1000 according to another embodiment may furtherinclude predetermined group identification information for identifying acorresponding reception group if the corresponding packet needs to bereceived by a plurality of apparatuses.

FIG. 11 is a flowchart for explanation of a method of controlling powertransmission in a wireless power transmitter according to an embodiment.

Upon receiving a negotiation request packet from the wireless powerreceiver, the wireless power transmitter may transmit a grant packet andmay enter the negotiation phase 440.

Referring to FIG. 11, in the negotiation phase 440, the wireless powertransmitter may receive an FOD status packet from the wireless powerreceiver (S1110).

For example, as shown in FIG. 10, the wireless power transmitter mayreceive the FOD status packet having the reference quality factor value1031 in the message 1030 field.

The foreign object detection in the negotiation phase 440 is a procedureof comparing a reference value received from a receiver and a measuredvalue and the reference value and the measured value may be varioustypes of parameters.

For example, the reference value and the measured value may include aresonant frequency, resistance, inductance, and the like without beinglimited thereto.

The wireless power transmitter 510 may measure measured equivalentseries resistance (ESR) ESR_measured using a pre-stored measured peakfrequency PF_measured and a measured quality factor value Q_measured.

Here, the ESR may a series resistance component parasitic on a capacitoror the like in an RLC series circuit. An actual capacitor and inductorused in an electric circuit are not an ideal component having onlycapacitance or inductance. However, when a capacitor and an inductor areconnected in series to a resistor, the capacitor and the inductor may bevery approximately considered as an ideal capacitor and inductor. Theresistor may be defined as equivalent series resistance (ESR).

The wireless power transmitter 510 may calculate reference ESRESR_reference using the received reference peak frequency PF_referenceand the reference quality factor value Q_reference.

The wireless power transmitter 510 may detect the foreign object usingESR_measured and ESR_reference. For example, the wireless powertransmitter 510 may compare a radio of ESR_reference and ESR_measuredwith a predetermined threshold value to determine whether the foreignobject is present.

The wireless power transmitter may transmit an ACK response or a NACKresponse to the wireless power receiver according to the foreign objectdetection result.

Upon receiving the NACK response from the wireless power transmitter,the wireless power receiver may perform control not to supply power ofpredetermine intensity or greater to an electronic device (orbattery/load) through an output terminal until the wireless powertransmitter completely stops power transmission. Here, the power ofpredetermine intensity or greater may be 5 W as a reference withoutbeing limited thereto.

Hereinafter, a relationship of ESR, the quality factor value Q, and afrequency will be described.

The quality factor value Q in the ideal RLC series circuit and a tunedradio frequency (TRF) receiver may be calculated according to Equation 1below.

$\begin{matrix}{Q = {{R\sqrt{\frac{L}{C}}} = \frac{w_{0}L}{R}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

Here, R, L, and C are resistance, inductance, and capacitance,respectively, w₀=2πf₀ is satisfied, and f₀ is a resonant frequency.

According to

${f_{0} = \frac{1}{2\pi \sqrt{LC}}},{Q = \frac{1}{w_{0}{CR}}}$

is satisfied.

ESR is AC resistance that is always measured at a standard frequency,and high ESR may increase aging and heating of a component, and ripplecurrent.

${ESR} = \frac{1}{w_{0}{CQ}}$

may be calculated.

Accordingly, in the above embodiment, ESR_reference is calculated as

$\frac{1}{2\pi \; {PF}_{ref}{CQref}},$

as

$\frac{1}{2\pi \; {Pf}_{measured}{CQ}_{measured}}.$

Q_(measured): Q-factor measured by a wireless charger

Pf_(measured): Peak frequency measured by a wireless charger

Q_(ref): Reference Q-factor in a wireless charger type coil (in thestate in which a receiver is placed and a foreign object is not present)

Pf_(ref): Reference peak frequency in a wireless charger type coil (inthe state in which a receiver is placed and a foreign object is notpresent)

C: Capacitance of a resonant capacitor of a wireless charger

In this case, a ratio of ESR_reference and ESR_measured may becalculated as follows.

$\frac{ESR\_ reference}{ESR\_ measured} = {\frac{1}{\frac{2{\pi \cdot \; {Pf}_{ref} \cdot C \cdot {Qref}}}{\frac{1}{2{\pi \cdot \; {Pf}_{measured} \cdot C \cdot Q_{measured}}}}} = \frac{{Pf}_{measured} \cdot Q_{measured}}{{Pf}_{ref} \cdot Q_{ref}}}$$\mspace{79mu} {{\frac{ESR\_ reference}{ESR\_ measured} - 1} = {\frac{{Pf}_{measured} \cdot Q_{measured}}{{Pf}_{ref} \cdot Q_{ref}} - 1}}$

The wireless power transmitter according to an embodiment may determinewhether the foreign object is present when a ratio of ESR_reference andESR_measured is greater than a predefined ratio threshold value. Here,the ratio threshold value may be determined according to an experimentresult. For example, when

$\frac{{Pf}_{measured}Q_{measured}}{{Pf}_{ref}Q_{ref}} - 1$

is greater than 0.2, the foreign object may be determined to be present.

The following description will be given in terms of an example in whichthe wireless power transmitter determines whether the foreign object ispresent based on the measured quality factor value and the determinedquality factor threshold value.

The wireless power transmitter may determine whether the foreign objectis present (S1120). Here, the wireless power transmitter may detect anobject in the selection phase 410 and may then compare a quality factorvalue measured prior to entrance into the ping phase 420 and a qualityfactor threshold value determined based on the reference quality factorvalue received in the negotiation phase 440 to determine whether theforeign object is present.

As the determination result, when the foreign object is not present, thewireless power transmitter may transmit a first response signal to thecorresponding wireless power receiver (S1130). Here, the first responsesignal may be an ACK signal.

The wireless power transmitter may transmit the first response signaland may then perform a first power transmission control procedure(S1140).

As the determination result of operation 1120, when the foreign objectis present, the wireless power transmitter may transmit a secondresponse signal (S1150). Here, the second response signal may be a NACKsignal.

The wireless power transmitter may transmit the second response signaland may then perform a second power transmission control procedure(S1160).

Here, the detailed configuration of the first power transmission controlprocedure and the second power transmission control procedure would beobvious through the following description of drawings.

FIG. 12 is a flowchart for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment.

Upon receiving a negotiation request packet from the wireless powerreceiver, the wireless power transmitter may transmit a grant packet toenter the negotiation phase 440.

Referring to FIG. 12, in the negotiation phase 440, the wireless powertransmitter may receive an FOD status packet from the wireless powerreceiver (S1201). For example, as shown in FIG. 10, the wireless powertransmitter may receive the FOD status packet having the referencequality factor value 1031 in the message 1030 field.

The wireless power transmitter may determine whether the foreign objectis present (S1202). Here, the wireless power transmitter may detect anobject in the selection phase 410 and may then compare a quality factorvalue measured prior to entrance into the ping phase 420 and a qualityfactor threshold value determined based on the reference quality factorvalue received in the negotiation phase 440 to determine whether theforeign object is present.

As the determination result, when the foreign object is not present, thewireless power transmitter may transmit a first response signal to thecorresponding wireless power receiver (S1203). Here, the first responsesignal may be an ACK signal.

Upon receiving the first response signal, the wireless power transmittermay perform the first power transmission control procedure (S1140).

Hereinafter, the first power transmission control procedure S1140 willbe described in detail.

Upon determining that the foreign object is not present, the wirelesspower transmitter may set guaranteed power to maximum or potentialpower. For example, the maximum power may be 15 W without being limitedthereto, and the maximum power may be greater than 15 W according to aconfiguration aspect and design of a wireless charger.

In the negotiation phase, the wireless power transmitter may transmit atransmitter power capability packet including the set guaranteed powerto the wireless power receiver. Thus, the wireless power receiver maydetermine required power within guaranteed power of the transmitter.

The wireless power transmitter may receive the guaranteed power packetincluding information guaranteed power (or required power) requested bythe wireless power receiver (S1204).

The wireless power transmitter may receive the end negotiation packetfrom the wireless power receiver (S1205).

Upon receiving the end negotiation packet, the wireless powertransmitter may enter the calibration phase 450 from the negotiationphase 440.

The wireless power transmitter may enter the calibration phase 450 toperform a calibration procedure (S1206).

When the calibration procedure is completed, the wireless powertransmitter may enter the power transfer phase 460 to initiate charging(S1207).

As the determination result of operation S1202, when the foreign objectis present, the wireless power transmitter may transmit a secondresponse signal in response to the FOD status packet (S1208). Here, thesecond response signal may be a NACK signal.

Upon receiving the second response signal in response to the FOD statuspacket, the wireless power receiver may perform the second powertransmission control procedure S1160.

Hereinafter, the second power transmission control procedure S1160 willbe described in detail.

Upon determining that the foreign object is present, the wireless powertransmitter may limit guaranteed power to the first power—that is,minimum guaranteed power (e.g., 5 W)—and may transmit power (S1209). Thewireless power transmitter may determine that the foreign object ispresent and may determine whether the foreign object is present based ona boundary value (or reference value) of preset power loss in the statein which the guaranteed power is set to 5 W. Here, 5 W is predeterminedminimum power in a transmission and reception time period, and thus thewireless power transmitter may set a solid reference and may determinethe foreign object. The foreign object detection method based on powerloss and another type foreign object detection method may also beapplied.

Here, the first power may be guaranteed power corresponding to the firstpower transfer mode. For example, the first power may be set to 5 Wwithout being limited thereto, and the first power may also be set tospecific power that is smaller than 5 W. In this case, it may be notedthat the wireless power transmitter does not stop transmission of awireless power signal.

The wireless power transmitter may receive the guaranteed power packet(S1210). Here, the guaranteed power packet may include information onrequired power determined within available guaranteed power of thewireless power transmitter by the wireless power receiver.

Upon receiving the end negotiation packet from the wireless powerreceiver, the wireless power transmitter may terminate the negotiationphase 440 and may enter the power transfer phase 460 to perform chargingwith the set first power (S1212).

In the above embodiment of FIG. 12, the case in which the wireless powertransmitter receives the guaranteed power packet and the end negotiationpacket during the second power transmission control procedure S1160 hasbeen described, but this is merely an embodiment, and according toanother embodiment, at least one of the guaranteed power packet or theend negotiation packet may not be received by the wireless powertransmitter.

The wireless power transmitter according to an embodiment may notperform the calibration phase 450 during the second power transmissioncontrol procedure S1160.

Here, the calibration phase 450 may be a procedure of comparingtransmission power of the transmitter and the reception power of thereceiver in order to accurately measure the transmission power and thereception power between the transmitter and the receiver, and a value ofpower loss.

In this case, in the second power transfer mode in which guaranteedpower is equal to or greater than 5 W, power loss is changed astransmission power is increased, and thus a power loss value may bepredicted (calculated) and the predicted value may be applied when thetransmission power is changed, thereby more accurately calculating powerloss. However, the first power transfer mode in which guaranteed poweris 4 W that is minimum power may be operated and fixed power may be setto a target, and thus it may not be required to perform the separatecalibration phase 450.

When at least one of transmission power or reception power, or powerloss is calibrated in the state in which the foreign object is present,calibration is performed under influence of the foreign object, and thuseven if the foreign object is actually present, the possibility that thewireless power transmitter determines that the foreign object is notpresent may be increased. That is, the accuracy of determining theforeign object may be lowered.

According to the disclosure, control may be performed not to perform thecalibration phase 450 during the second power transmission controlprocedure S1160, and thus the accuracy of detecting the foreign objectmay be increased.

FIG. 13 is a diagram for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment.

Referring to FIG. 13, the wireless power transmitter may completelyperform the second power transmission control procedure S1160 to enterthe power transfer phase 460 (S1310).

The wireless power transmitter may measure (or calculate or estimate)power loss based on the received power packet received during powertransmission—that is, charging—in the power transfer phase 460 (S1320).

Hereinafter, for convenience of description, the case in which thewireless power transmitter measures power loss will be described, butthis is merely an embodiment, and it may be noted that power loss iscalculated or estimated based on the measured result of transmissionpower in a wireless power transmission end and the measured result ofthe reception power received from a wireless power reception end.

For example, power loss may be measured (or estimated) based on thereceived power packet fed back from the wireless power receiver for apredetermined time period during charging in the power transfer phase460.

Here, the power loss may include at least one of first power lossmeasured based on a first reception power value in the state in whichthe wireless power receiver is not connected to a battery (or a load) orsecond power loss measured based on a second reception power valuemeasured in the state in which the wireless power receiver is connectedto a battery (or a load).

For example, the wireless power transmitter may measure power losswhenever the received packet is received during a predeterminedperiod—for example, 10 minutes—and may determine an average value (asmallest value or a highest value) of the measured power loss as finalpower loss.

In another example, the wireless power transmitter may also measurepower loss to correspond N received power packets that are continuouslyreceived after entrance into the power transfer phase 460.

The wireless power transmitter may determine whether the foreign objectis present based on the measured power loss (S1330).

For example, when the measured power loss is greater than apredetermined power loss threshold value, the wireless power transmittermay determine that the foreign object is present. In contrast, when themeasured power loss is equal to less than the predetermined power loss,the wireless power transmitter may determine that the foreign object isnot present

In another example, when the power loss estimated to corresponding to Nreceived power packets that are continuously received after entranceinto the power transfer phase falls within the predetermined power lossthreshold value, the wireless power transmitter may determine that theforeign object is not present. When the power loss falls within thethreshold value for a specific time period, or after a specific timeperiod elapses, even if the power loss falls within the threshold value,the wireless power transmitter may also determine that the foreignobject is not present.

In contrast, when the power loss estimated to correspond to at least onereceived power packet among N received power packets that arecontinuously received after entrance into the power transfer phase isgreater than a predetermined power loss threshold value, the wirelesspower transmitter may determine that the foreign object is present.

As the determination result, when the foreign object is present, thewireless power transmitter may stop power transmission and may enter theselection phase (S1340 and S1350).

As the determination result of operation 1330, when the foreign objectis not present, the wireless power transmitter may enter a renegotiationphase and may renegotiate a power transfer contract with the wirelesspower receiver (S1360). In this case, the negotiated guaranteed powermay be equal to or greater than 5 W.

According to the renegotiation result, the wireless power transmittermay enter the power transfer phase 460 again and may continuouslyperform charging on the corresponding wireless power receiver. Here,after the renegotiation, the wireless power transmitter may transmitpower between the first power and the second power and may performcharging. Here, the first power may be 5 W and the second power may be15 W, but this is merely an embodiment, and intensity of the secondpower may be greater than or smaller than 15 W.

For example, when the foreign object is not detected after entrance intothe power transfer phase, the wireless power transmitter may change thefirst power transfer mode to the second power transfer mode throughrenegotiation to increase intensity of transmission power and to reducea charging time.

FIG. 14 is a diagram for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment.

Referring to FIG. 14, the wireless power transmitter may completelyperform the second power transmission control procedure S1160 and mayenter the power transfer phase 460 (S1410).

The wireless power transmitter may measure a temperature change duringpower transmission in the power transfer phase 460 (S1420).

For example, in the power transfer phase 460, the wireless powertransmitter may measure a ratio of an internal temperature change amountor a temperature change during a unit time during power transmission.Here, a position of the wireless power transmitter, at which thetemperature change is measured, may be a transmission coil of thetransmission antenna 640 without being limited thereto, and thetemperature change may also be measured at another position of thewireless power transmitter—for example, a control circuit board includedin the wireless power transmitter, and a charging bed—of the wirelesspower transmitter according to a design of one of ordinary skill in theart.

The wireless power transmitter according to another embodiment may alsoreceive temperature information measured by the wireless power receiverat a predetermined period during power transmission. The wireless powertransmitter may also measure the temperature change based on thetemperature information received from the wireless power receiver.

The wireless power transmitter according to another embodiment maydetermine a final temperature change based on the internally measuredfirst temperature change and the second temperature change that ismeasured based on the temperature information received from the wirelesspower receiver.

The wireless power transmitter may determine whether the foreign objectis present based on the measured temperature change (S1430). Forexample, when the measured temperature change is greater than apredetermined temperature change threshold value, the wireless powertransmitter may determine that the foreign object is present.

In contrast, when the measured temperature change is equal to or lessthan the predetermined temperature change threshold value, the wirelesspower transmitter may determine that the foreign object is not present.

As the determination result, when the foreign object is present, thewireless power transmitter may stop power transmission and may enter theselection phase (S1440 and S1450).

As the determination result of operation 1430, when the foreign objectis not present, the wireless power transmitter may enter therenegotiation phase to renegotiate a power transfer contract with thewireless power receiver (S1360).

As the renegotiation result, the wireless power transmitter may enterthe power transfer phase 460 again and may continuously performcharging.

For example, when the foreign object is not detected after entrance intothe power transfer phase, the wireless power transmitter may change thefirst power transfer mode to the second power transfer mode viarenegotiation to increase intensity of transmission power and to reducea charging time. The wireless power transmitter may transmit powerbetween the first power and the second power in the second powertransfer mode. Here, the first power may be 5 W and the second power maybe 15 W, but this is merely an embodiment, and the second power may besmaller than or greater than 15 W according to a design of one ofordinary skill in the art and a configuration aspect of the wirelesspower transmitter.

FIG. 15 is a diagram for explanation of a method of controlling powertransmission in a wireless power transmitter according to anotherembodiment.

Referring to FIG. 15, the wireless power transmitter may completelyperform the second power transmission control procedure S1160 and mayenter the power transfer phase 460 (S1510).

The wireless power transmitter may measure power loss of the receivedpower packet received during power transmission in the power transferphase 460 (S1520).

For example, power loss may be measured based on the received powerpacket fed back from the wireless power receiver during charging in thepower transfer phase 460.

Here, the power loss may include at least one of first power lossmeasured based on a first reception power value in the state in whichthe wireless power receiver is not connected to a battery (or a load) orsecond power loss measured based on a second reception power valuemeasured in the state in which the wireless power receiver is connectedto a battery (or a load).

The wireless power transmitter may determine whether the foreign objectis present based on the measured power loss (S1530). For example, whenthe measured power loss is greater than a predetermined power lossthreshold value, the wireless power transmitter may determine that theforeign object is present. In contrast, when the measured power loss isequal to or less than a predetermined power loss threshold value, thewireless power transmitter may determine that the foreign object is notpresent.

As the determination result, when the foreign object is present, thewireless power transmitter may stop power transmission and may enter theselection phase (S1540 and S1550).

As the determination result of operation 1530, when the foreign objectis not present, the wireless power transmitter may measure a temperaturechange during power transmission in the power transfer phase 460(S1560).

For example, in the power transfer phase 460, the wireless powertransmitter may measure a ratio of an internal temperature change amountor a temperature change during a unit time during power transmission.Here, a position of the wireless power transmitter, at which thetemperature change is measured, may be in the vicinity of thetransmission coil without being limited thereto, and the temperaturechange may also be measured at another position of the wireless powertransmitter according to a design of one of ordinary skill in the art.

The wireless power transmitter according to another embodiment may alsoreceive temperature information measured by the wireless power receiverat a predetermined period during power transmission. The wireless powertransmitter may also measure the temperature change based on thetemperature information received from the wireless power receiver.

The wireless power transmitter according to another embodiment maydetermine a final temperature change based on the internally measuredfirst temperature change and the second temperature change that ismeasured based on the temperature information received from the wirelesspower receiver.

The wireless power transmitter may determine whether the foreign objectis present based on the measured temperature change (S1570). Forexample, when the measured temperature change is greater than apredetermined temperature change threshold value, the wireless powertransmitter may determine that the foreign object is present.

In contrast, when the measured temperature change is equal to or lessthan the predetermined temperature change threshold value, the wirelesspower transmitter may determine that the foreign object is not present.

As the determination result, when the foreign object is present, thewireless power transmitter may stop power transmission and may enter theselection phase (S1540 and S1550).

As the determination result of operation 1570, when the foreign objectis not present, the wireless power transmitter may enter therenegotiation phase to renegotiate a power transfer contract with thewireless power receiver (S1580). As the renegotiation result, thewireless power transmitter may enter the power transfer phase 460 againand may continuously perform charging.

For example, when the foreign object is not detected after entrance intothe power transfer phase, the wireless power transmitter may change thefirst power transfer mode to the second power transfer mode viarenegotiation to increase intensity of transmission power and to reducea charging time.

In the above embodiment of FIG. 15, the case in which the wireless powertransmitter performs the foreign object detection procedure based onpower loss and then performs the foreign object detection procedurebased on a temperature change according to the determination result hasbeen described, but this is merely an embodiment, and according toanother embodiment, the wireless power transmitter may perform theforeign object detection procedure based on a temperature change and maythen perform the foreign object detection procedure based on power lossaccording to the determination result.

FIG. 16A is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter and a receiver have the same version.

In the following description of embodiments, it may be noted that thesecond version is a higher-ranking and more recently released versionthan the first version.

In detail, FIG. 16A is a flowchart for explanation of a method ofcontrolling wireless power transmission based on foreign objectdetection when both the transmitter and the receiver have a low-rankingversion, that is, a first version—for example, 1.2 V—. Here, the versionmay be based on the WPC Qi standard.

Referring to FIG. 16A, when entering the negotiation phase, a firstversion transmitter 1610 may receive an FOD status packet from a firstversion receiver 1620 (S1601).

The first version transmitter 1610 may determine whether the foreignobject is present based on the received FOD status packet, and as thedetermination result, when the foreign object is present, the firstversion transmitter 1610 may transmit a NACK signal to the first versionreceiver 1620 (S1602).

Upon receiving a NACK response signal to an FOD status packet, the firstversion receiver 1620 may not transmit any packet or may transmit aspecific packet (S1603).

Upon transmitting a NACK signal to the first version receiver 1620, thefirst version transmitter 1610 may stop power transmission within apredetermined time period—for example, 5 seconds—(S1604). In this case,the first version transmitter 1610 may disregard any packet receivedfrom the first version receiver 1620.

FIG. 16B is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter and a receiver have different versions.

In detail, FIG. 16B is a flowchart for explanation of a method ofcontrolling wireless power transmission based on foreign objectdetection when the receiver has a higher-ranking version than thetransmitter.

Referring to FIG. 16B, upon entering the negotiation phase, a firstversion transmitter 1630 may receive an FOD status packet from a secondversion receiver 1640 (S1605).

The first version transmitter 1630 may determine whether the foreignobject is present based on the received FOD status packet, when theforeign object is present as the determination result, the first versiontransmitter 1630 may transmit a NACK signal to the second versionreceiver 1640 (S1606).

Upon receiving a NACK response signal to the FOD status packet, thesecond version receiver 1640 may transmit a general request packet (GRP)including power transmitter capability (PTC) information to the firstversion transmitter 1630 (S1607).

Upon transmitting a NACK signal to the second version receiver 1640having a higher-ranking version than the first version transmitter 1630,the first version transmitter 1630 may disregard the received GRP andmay stop power transmission within a predetermined time period—forexample, 5 seconds—(S1608).

FIG. 16C is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter and a receiver have the same version.

In detail, FIG. 16C is a flowchart for explanation of a method ofcontrolling wireless power transmission based on foreign objectdetection when both the transmitter and the receiver have a high-rankingversion, that is, a second version—for example, 1.3 V—.

Referring to FIG. 16C, upon entering the negotiation phase, a secondversion transmitter 1650 may receive an FOD status packet from a secondversion receiver 1660 (S1609).

The second version transmitter 1650 may determine whether the foreignobject is present based on the received FOD status packet, and as thedetermination result, when the foreign object is present, the secondversion transmitter 1650 may transmit a NACK signal to the secondversion receiver 1660 (S1610).

Upon receiving a NACK response signal to the FOD status packet, thesecond version receiver 1660 may transmit a general request packet (GRP)including power transmitter capability (PTC) information to the secondversion transmitter 1650 (S1611).

Upon receiving the GRP from the second version receiver 1660 having thesame version as that of the second version transmitter 1650, the secondversion transmitter 1650 may transmit a PTC packet in which guaranteedpower is set to the first power, to the second version receiver 1660(S1612).

In this case, the second version receiver 1660 may transmit a specialrequest packet in which guaranteed power is set to the first power, tothe second version transmitter 1650 (S1613).

The second version transmitter 1650 may transmit an ACK signal inresponse to the special request packet (S1614) and may enter the powertransfer phase to set the guaranteed power to the first power and toperform charging (S1615).

The wireless power transmitter according to the above embodiment of FIG.16C may advantageously downward-adjust the guaranteed power and maystably maintain a charging state even if the foreign object is detectedin the negotiation phase.

In the above embodiment of FIG. 16C, upon receiving a special requestpacket in which guaranteed power is set to be larger than the firstpower in operation 1613 operation, the second version transmitter 1650may transmit a NACK response to the second version receiver 1660 inresponse to the special request packet.

FIG. 16D is a flowchart for explanation of a method of controllingwireless power transmission based on foreign object detection when atransmitter has a higher-ranking version than a receiver.

In detail, FIG. 16D is a flowchart for explanation of a method ofcontrolling wireless power transmission during foreign object detectionto maintain backward compatibility when a version of the receiver is afirst version—for example, 1.2 V—that is a lower-ranking version thanthe transmitter.

Referring to FIG. 16D, upon entering the negotiation phase, a secondversion transmitter 1670 may receive an FOD status packet from a firstversion receiver 1680 (S1616).

The second version transmitter 1670 may determine whether the foreignobject is present based on the received FOD status packet, and as thedetermination result, when the foreign object is present, the secondversion transmitter 1670 may transmit a NACK signal to the first versionreceiver 1680 (S1617).

For example, upon receiving a NACK response signal to an FOD statuspacket, the first version receiver 1680 may transmit the general requestpacket (GRP) including the power transmitter capability (PTC)information to the second version transmitter 1670 (S1618). In anotherexample, upon receiving an NACK response signal to the FOD status packetaccording to a type of the receiver, the first version receiver 1680 maynot transmit any packet to the second version transmitter 1670.

Upon transmitting a NACK signal to the first version receiver 1680having a lower-ranking version than the second version transmitter 1670,the second version transmitter 1670 may transmit a PTC packet in whichguaranteed power is set to the first power, to the first versionreceiver 1680 (S1619).

For example, the first version receiver 1680 may transmit a specialrequest packet in which guaranteed power is set to the first power, tothe second version transmitter 1670 (S1620). In another example, uponreceiving a NACK response signal to the FOD status packet according to atype of the receiver, the first version receiver 1680 may not transmitany packet to the second version transmitter 1670.

The second version transmitter 1650 may transmit a NACK signal inresponse to the special request packet (S1621) and may stop powertransmission within a predetermined time period—for example, 5 secondswithout being limited thereto —. The second version transmitter 1650 maytransmit a NACK signal in response to the special request packet, andthus the first version receiver 1680 may be prevented from entering acalibration phase after the negotiation phase is terminated.

Effects of the method, the apparatus, and the system according to thedisclosure will be described below.

The disclosure may advantageously provide a method and apparatus forcontrolling wireless power transmission for wireless charging.

The disclosure may advantageously provide a wireless power transmitterfor more accurately detecting a foreign object.

The disclosure may advantageously provide a method and apparatus forcontrolling wireless power transmission for minimizing foreign objectdetection error to prevent unnecessary stop of charging.

The disclosure may advantageously provide a wireless power transmitterfor preventing a device from being damaged due to a foreign object andfor seamless charging through adaptive transmission power controlaccording to whether the foreign object is present.

In addition, the disclosure may advantageously provide a wireless powertransmitter for stably transmitting wireless power in a wide rangeaccording to a type of a receiver and a power transmission environment.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the embodiments of the disclosureare not limited to what has been particularly described hereinabove andother advantages of the disclosure will be more clearly understood fromthe detailed description taken in conjunction with the accompanyingdrawings.

The methods according to the above embodiments can be embodied as aprogram to be executed in a computer and can be stored in a computerreadable recording medium. Examples of the computer readable recordingmedium include read-only memory (ROM), random-access memory (RAM),CD-ROMs, magnetic tapes, floppy discs, optical data storage devices,etc.

The computer readable recording medium can also be distributed overnetwork coupled computer systems so that the computer readable code isstored and executed in a distributed fashion. Also, functional programs,codes, and code segments for accomplishing the embodiments can be easilyconstrued by programmers skilled in the art to which the embodimentspertain.

Those skilled in the art will appreciate that the embodiments of thedisclosure may be carried out in other specific ways than those setforth herein without departing from the spirit and essentialcharacteristics of the embodiments.

The above embodiments are therefore to be construed in all aspects asillustrative and not restrictive. The scope of the embodiments should bedetermined by the appended claims and their legal equivalents, not bythe above description, and all changes coming within the meaning andequivalency range of the appended claims are intended to be embracedtherein.

What is claimed is:
 1. A method of controlling wireless powertransmission of a wireless power transmitter, the method comprising: afirst packet reception phase of receiving a foreign object detectionstatus packet; a first determination phase of determining whether theforeign object is present based on the foreign object detection statuspacket; and a power control phase of controlling power based on adetermination result of the first determination phase, wherein the powercontrol phase includes: performing control in a first power transfermode for transmitting first power upon determining that the foreignobject is present as the determination result of the first determinationphase; and performing control in a second power transfer mode fortransmitting second power upon determining that the foreign object isnot present as the determination result of the first determinationphase.
 2. The method of claim 1, wherein: the second power is greaterthan the first power; and power between the first power and the secondpower is increasingly or decreasingly transmitted based on a change in apower transmission environment in the second power transfer mode.
 3. Themethod of claim 2, wherein the first power is 5 W.
 4. The method ofclaim 3, wherein the second power is 15 W.
 5. The method of claim 1,further comprising a second determination phase of determining whetherthe foreign object is present in the first power transfer mode.
 6. Themethod of claim 5, wherein the second determination phase includes atleast one of: a third determination phase of determining whether theforeign object is present based on loss of transmission power; or afourth determination phase of determining whether the foreign object ispresent based on a temperature change.
 7. The method of claim 6, whereinthe third determination phase includes: measuring intensity of thetransmission power; receiving information on intensity of receptionpower corresponding to the transmission power from a wireless powerreceiver; estimating power loss based on a difference value between theintensity of the transmission power and the intensity of the receptionpower; and comparing the estimated power loss with a predetermined powerloss reference value to determine whether the foreign object is presentfor a predetermined time period.
 8. The method of claim 6, wherein thefourth determination phase includes: measuring temperature of a chargingarea; calculating a temperature change for a predetermined time periodbased on the measured temperature; and comparing the calculatedtemperature change with a predetermined temperature change referencevalue to determine whether the foreign object is present.
 9. The methodof claim 5, wherein, as a determination result of the seconddetermination phase, when the foreign object is determined to bepresent, power transmission is stopped, and as the determination of thesecond determination phase, when the foreign object is not determined tobe present, the first power transfer mode is changed to the second powertransfer mode.
 10. A method of controlling wireless power transmissionof a wireless power transmitter, the method comprising: a first packetreception phase of receiving a foreign object detection status packet; afirst determination phase of determining whether the foreign object ispresent based on the foreign object detection status packet; a phase oftransmitting first power upon determining that the foreign object ispresent as a determination result of the first determination phase; aphase of transmitting power between the first power and the second powerwhen the foreign object is not present as the determination result ofthe first determination phase; and a second determination phase ofdetermining whether the foreign object is present based on loss oftransmission power in the phase of transmitting the first power.
 11. Awireless power transmitter comprising: an antenna configured towirelessly transmit power; a demodulator configured to demodulate asignal including a foreign object detection status packet received fromthe antenna; and a controller configured to determine whether theforeign object is present, wherein the controller performs a firstdetermination phase of determining whether the foreign object is presentbased on the foreign object detection status packet, performs control totransmit first power upon determining that the foreign object is presentas a result of the first determination phase, and performs control totransmit power between the first power and the second power upondetermining the foreign object is not present as the determinationresult of the first determination phase.
 12. The wireless powertransmitter of claim 11, wherein the controller performs a seconddetermination phase of determining whether the foreign object is presentbased on the power loss during transmission of the first power upondetermining that the foreign object is present as a result of the firstdetermination phase.
 13. The wireless power transmitter of claim 12,wherein the controller determines intensity of transmission power,receives information on intensity of reception power corresponding tothe transmission power through the demodulator, estimates power lossbased on a difference value between the intensity of the transmissionpower and the intensity of the reception power, and compares theestimated power loss with a predetermined power loss reference value todetermine whether the foreign object is present.
 14. The wireless powertransmitter of claim 12, wherein as a determination result of the seconddetermination phase, when the foreign object is determined to bepresent, the controller stops power transmission, and as determinationof the second determination phase, when the foreign object is notdetermined to be present, the controller performs control to transmitpower between the first power and the second power.
 15. The wirelesspower transmitter of claim 11, wherein the second power is greater thanthe first power, and the first power is 5 W.